The invention concerns a closing unit for an injection molding machine, and a tie-bar-less injection molding machine having such a closing unit.
A closing unit of the general kind set forth is disclosed, for example, in DE 101 21 306 A1. The change in the orientation of the stationary mold mounting plate, that is caused per se by the closing force, is compensated in part by the support element and in part by the geometrical configuration of the free leg of the machine frame, to which the stationary mold mounting plate is connected. That design permits the stationary mold mounting plate to be fixedly mounted to the free leg of the machine frame and thus avoids the disadvantages of a pivotal mounting of the stationary mold mounting plate. The geometrical configuration required for that purpose for the free leg can be ascertained, for example, by calculation or experiments.
In the closing unit shown there, the support element comprises a compression bar which is in the form of an extension on the stationary mold mounting plate, and which extends in the direction of the longitudinal axis of the machine and which under the closing force presses loosely against a flexural beam extending transversely relative to the longitudinal axis of the machine. High line loadings occur between the compression bar and the flexural beam. The strong internal frictional effects of the support element, that are linked thereto, adversely affect the functionality of the closing unit due to tribocorrosion (fretting corrosion) and shorten the service life of the support element.
In addition, it has proven to be difficult to find satisfactory matching of upsetting by way of the compression bar and flexing by way of the flexural beam with that construction.